1. Field of the Invention:
The present invention relates to bone implants. More specifically, the invention relates to surgical implants for graft fixation in arthroscopic ligament repair in the knee using semitendinosus and gracilis tendon autografts.
2. Description of the Related Art:
When a ligament or tendon becomes detached from associated bone, surgery usually is required to re-secure the ligament or tendon. Often, a substitute ligament, or graft, is attached to the bone to facilitate re-growth and permanent attachment. Various methods of ligament graft attachment are known, including staples, suture over buttons, and interference screw fixation.
Various problems exist with the known fixation methods. Staples and suture buttons are disadvantageous because they often do not provide fixation sufficient to withstand the normal tensile loads. With suture button fixation, for example, a strand of suture couples the button and the substitute ligament. This strand becomes the "weakest link in the chain," and if the strand breaks, the ligament detaches.
A stronger graft attachment can be obtained by interference screw fixation, whereby an interference screw is used to wedge a graft bone block to the wall of a graft tunnel. See, e.g., U.S. Pat. Nos. 5,211,647, and 5,603,716, incorporated herein by reference.
Although interference screw attachment is more secure than using staples or suture buttons, it is sometimes neither possible nor desirable to provide such fixation, particularly in the femoral tunnel. In revision situations, for example, where a previous reconstruction has been performed, placing a second femoral tunnel close to the previous tunnel may not be indicated.
In other cases, a semitendinosus graft must be used because the previous reconstruction used the mid third patellar tendon. Although a bone-semitendinosus graft-bone construct may be prepared using a workstation as disclosed in U.S. Pat. No. 5,397,357, such a procedure is time consuming, and may be undesirable for other reasons.
A fixation technique which provides strong attachment of a semitendinosus graft in the femoral tunnel, using a transverse pin, is disclosed in U.S. Pat. No. 5,601,562, of common assignment with the present application. The transverse pin is inserted through a loop in a tendon graft. A threaded portion of the pin screws into the bone as the pin is advanced with rotation into the repair site. The technique is disadvantageous, however, because the graft can wrap around the pin as it is rotated. An improved loading technique is the subject of a co-pending U.S. patent application, attorney docket no. P/1493-147, which also claims the benefit of U.S. Provisional Application Ser. No. 60/037,610, filed Feb. 12, 1997.
Various endoscopic techniques and instruments relating to graft fixation are known in the prior art and can be used in the practice of the present invention as it relates to graft repair of knee ligaments, as follows: U.S. Pat. No. 5,320,636 to Schmieding discusses an endoscopic drill guide for graft tunnel location. U.S. Pat. No. Des. 378,780 illustrates a cannulated headed reamer as can be used in femoral socket formation. U.S. Pat. Nos. 5,269,786 and 5,350,383 disclose drill guides for location of bone tunnels.
The need exists for fixation devices that can be installed without rotation, and yet are removable.